All of my ebooks have a filename of the form
author1, author2, ... - [series seriesindex - ] title.*
and I have set up Calibre to read metadata from the filename.
Calibre, however, does not seem to split on ", ". How do I modify the regular expression under "Preferences"->"Tweaks" -> "Splitting multiple author names" (authors_split_regex) to add ", " as a possible separator?